IS MILK GOOD FOR ADULT CATS ?

When one wants to be nice with a cat, he is offered some milk. It is true that he usually appreciates it. However, one must be aware that not all cats are able to digest it properly. Tolerance to milk varies a lot according to individuals. Then, it is necessary to have a few practical ideas about how much milk it is possible to give to a cat, and what are the consequences of an excess.

The dry matter of the milk is very rich in fat, but because of its important dilution, it is very difficult to use it as the sole source of food for a cat. In fact, to meet the daily energetic requirements of a 4 kg cat with milk only, it would be necessary to give him almost either half a liter of crude milk (700 kcal/ liter) or 800 ml of half-skimmed milk (450 kcal/ liter) per day ! These volumes are obviously over its digestive ability. Consequently, the milk can only represent an eventual nutritional complement. Even as such, it will be tolerated only if the enzymes necessary for the hydrolysis of the different components of the milk are represented, in proper quantities.

Digestive tolerance to lactose

Lactose is the main carbohydrate of the milk. Queen's milk is rather rich in lactose (20 - 25 % on dry matter), but really poorer than cow's milk. During the first 5 weeks of its life, the kitten is well-adapted to digest lactose, thanks to the intestinal production of a specific enzyme, called lactase.

At weaning,75 to 90 % of the lactase production disappears rapidly. The lactase activity reaches the adult level around 12 weeks : then this level is 10 - 30 times less than in the newborn kitten. This loss of capacity to digest lactose happens even if the kitten still receives milk after weaning. According to individual cases, the critical level of tolerance of weaned cats towards lactose varies a lot. As an average, it represents roughly 1 - 2 g of lactose per kg of bodyweight.

When the lactasic capacity is overcome, stools are becoming loose, even haemorrhagic in some cases. In addition, it has been observed that an excess of lactose in the diet is responsible for a lower digestion of proteins. It can be explained by two main reasons:

proteins are less submitted to the enzymatic attack in the small intestine because the transit is accelerated ;

as lactose arrives undigested in the large intestine, it stimulates the growth of the bacterial flora, and proteins are incorporated by the bacteriological mass.

Conclusion

To prevent from milk intolerance, it is wiser not to distribute more than 1 g of lactose per kg to a cat as soon as he is weaned. It is the equivalent of 20 ml of milk maximum (crude or half-skimmed, it does not make any difference), per kg of bodyweight.

On the opposite, as cat is a carnivorous, he is perfectly able to digest casein, that represents about 80 % of the milk proteins. It is a very high-quality protein that can be used as a profitable complementary source of amino-acids in a cat food. The only one problem is its prohibitive cost (around 10 times the price of a classical source of animal proteins) that limits its incorporation.